Multifunction product (MFP)/Printer is a network-attached document production device that combines two or more of the copy, print, scan and fax functions. Generally, the printer contains a photosensitive assembly which is consisted of a photoconductive drum and a toner cartridge. The photoconductive drum is a photoconductor which can be charged to attract toner particles by way of electrostatic polarities, and then the toner particles can be fused or melted to the paper by a heating module. It is understood that the photosensitive assembly is consumable, thus the printer usually allows user to replace and install the photoconductive drum and the toner cartridge.